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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var arr = [1,2,3,4]
        // 1.算法实现
        var sum1 =0;
        for(var i=0;i<arr.length;i++){
            sum1 + = arr[i];
        }
        console.log(sum1);

        // 2.数组的方法
        var sum = arr.reduce((a,b)=>{
            return a+b;
        })
        console.log(sum);
    </script>
</body>
</html>